Datasheet

TPS7A8001
GND
EN FB
IN OUT
V
IN
V
OUT
4.7 Fm
Ceramic
V
EN
R
1
R
2
Optional1.0 Finputcapacitor.
Mayimprovesourceimpedance,
noise,orPSRR.
m
NR
Toavoidinrushcurrent,
itisrecommendedto
alwaysconnecta
1nFto10nFcapacitor
TPS7A80xx
GNDEN NR
IN OUT
V
IN
V
OUT
4.7 Fm
Ceramic
V
EN
Toavoidinrushcurrent,
itisrecommendedto
alwaysconnecta
1nFto10nFcapacitor
Optional1.0 Finputcapacitor.
Mayimprovesourceimpedance,
noise,orPSRR.
m
SNS
V =
OUT
x0.800
(R R
1 2
+ )
R
2
TPS7A80xx
www.ti.com SBVS135H –JUNE 2010–REVISED JANUARY 2013
APPLICATION INFORMATION
For the adjustable version (TPS7A8001), the voltage
The TPS7A80xx belongs to a family of new
on the FB pin sets the output voltage and is
generation LDO regulators that use innovative
determined by the values of R
1
and R
2
. The values of
circuitry to achieve wide bandwidth and high loop
R
1
and R
2
can be calculated for any voltage using the
gain, resulting in extremely high PSRR (over a 1MHz
formula given in Equation 1:
range) at very low headroom (V
IN
– V
OUT
). A noise
reduction capacitor (C
NR
) at the NR pin bypasses
noise generated by the bandgap reference in order to
(1)
improve PSRR, while a quick-start circuit fast-charges
Sample resistor values for common output voltages
this capacitor. This family of regulators offers sub-
are shown in Table 2. In Table 2, E96 series resistors
bandgap output voltages, current limit, and thermal
are used, and all values meet 1% of the target V
OUT
,
protection, and is fully specified from –40°C to
assuming resistors with zero error. For the actual
+125°C.
design, pay attention to any resistor error factors.
Figure 31 shows the basic circuit connections for the
Using lower values for R
1
and R
2
reduces the noise
fixed voltage options. Figure 32 gives the connections
injected from the FB pin.
for the adjustable output version (TPS7A8001).
Table 2. Sample 1% Resistor Values for Common
Output Voltages
V
OUT
R
1
R
2
0.8V 0Ω (Short) 10.0kΩ
1.0V 2.49kΩ 10.0kΩ
1.2V 4.99kΩ 10.0kΩ
1.5V 8.87kΩ 10.0kΩ
1.8V 12.5kΩ 10.0kΩ
2.5V 21.0kΩ 10.0kΩ
3.3V 30.9kΩ 10.0kΩ
5.0V 52.3kΩ 10.0kΩ
Figure 31. Typical Application Circuit
Input and Output Capacitor Requirements
(Fixed Voltage Versions)
Although an input capacitor is not required for
stability, it is good analog design practice to connect
a 0.1μF to 1.0μF low equivalent series resistance
(ESR) capacitor across the input supply near the
regulator. This capacitor counteracts reactive input
sources and improves transient response, noise
rejection, and ripple rejection. A higher-value
capacitor may be necessary if large, fast rise-time
load transients are anticipated or if the device is
located several inches from the power source. If
source impedance is not sufficiently low, a 0.1μF
input capacitor may be necessary to ensure stability.
The TPS7A80xx is designed to be stable with
standard ceramic capacitors of capacitance values
4.7μF or larger. This device is evaluated using a
4.7μF ceramic capacitor of 10V rating, 10%
Figure 32. Typical Application Circuit
tolerance, X5R type, and 0805 size (2.0mm x
(Adjustable Voltage Version)
1.25mm).
X5R- and X7R-type capacitors are highly
recommended because they have minimal variation
in value and ESR over temperature. Maximum ESR
should be <1.0Ω.
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